Systems and methods for joining components by riveting

ABSTRACT

A riveting system, for use in mechanically linking adjacent workpieces, including a rivet having a height greater than a sum of thicknesses, measured along a line of riveting, of the workpieces being linked, so that the rivet can pass fully through the workpieces. The system also includes a riveting die, which may be a separate product. The die includes a protrusion extending from a peak toward a transition point; and a trough having a trough surface. The trough surface includes a trough inner wall, extending from the transition point to a trough bottom, and a trough outer wall, extending from the trough bottom to a trough outer edge. The technology also includes computerized systems for comparing a load-displacement profile of riveting to a pre-set profile to determine whether the riveting was performed properly.

TECHNICAL FIELD

The present technology relates generally to systems and methods forjoining parts or workpieces and, more specifically, to systems andmethods for interlocking components using a riveting system including auniquely configured die and rivet. The die and rivet are configured tocause a distal edge or tip of the rivet to, after being forced throughboth components, turn upwards toward the workpieces, creating amechanical hook locking the components together.

BACKGROUND OF THE DISCLOSURE

In industries such as consumer electronics, home products andappliances, farming, construction equipment, transportation systems,automotive, aeronautical, and nautical, various manufacturing materialssuch as aluminum are joined to form relatively lightweight connectedparts. Polymeric composites are also being connected to metals or otherpolymers.

A manufacturer can select materials having favorable characteristics,such as being lightweight, highly-conformable or shapeable, strong,durable, or having a desired texture or color by combining some polymeror composite materials with other materials. An article of manufacturemay include various components (e.g., exterior, interior, or decorativefeatures) where materials are selected and configured to withstand, forexample, a hot and/or chemically aggressive environment or for paintingor chemical resistance over time.

With the increased use of polymers and other low-mass materials,compression molding and post-mold joining techniques, such as laserwelding and ultrasonic welding, are also being used more commonly.

Processes for joining similar or dissimilar materials include mechanicaljoining (e.g., bolts and rivets), fusion joining (e.g., fusion arcwelding and laser welding), solid-state joining (e.g., friction-stirwelding and ultrasonic welding), brazing and soldering, and adhesivebonding, among others.

Joining materials robustly and without great expense is a challenge.Considerations include chemical, mechanical, and thermal behaviors ofmaterials being joined. When designing a dissimilar-material joint, forinstance, factors such as, but not limited to, material thicknesses,surface energy, differences in melting temperature, and thermalexpansion/contraction of each material, must be taken intoconsideration. Differences in material properties of dissimilarmaterials make weld joining especially challenging and in some casesimpossible.

Turning to the figures, and more particularly to the first figure, FIG.1 illustrates a conventional rivet-joining system 100 in use joining afirst workpiece 110 to a second workpiece 120.

The system 100 includes a riveting machine 130 including a body 132 anda piston or punch 134 positioned adjacent and movably with respect tothe machine body 132. The system 100 includes a base 140, a die 150, anda rivet 160.

In operation, the machine body 132 is positioned adjacent the firstworkpiece 110 of the workpieces, as indicated by arrow 133 in FIG. 1.

The rivet 160 is positioned between the punch 134 and the firstworkpiece 110. The punch 134 pushes down on the rivet 160, as indicatedby arrow 180, forcing distal tips 162 of the rivet 160 to pierce theworkpieces 110, 120, first through a proximate one 110 of the workpieces110, 120, beyond an interface 115 between the two workpieces 110, 120,and into a distal one 120 of the workpieces 110, 120.

Designers of conventional techniques have had to choose between morecracks or less rivet flaring, each of which lowers joint quality.

Shortcomings of such techniques include the joint having less strengththan desired. Traditional techniques also use relatively short rivets,which do not reach through the lower, second workpiece 120. Jointstrength is lower than desired when the rivet 160 is kept to shallowdepths and not enabled to flare.

Undesired joint strength can also result from unacceptable levels ofcracking (e.g., cracks 117) created in the riveting process. Cracking,including micro-cracks and delamination within the workpieces, ispossible especially for workpiece materials having relatively lowductility, such as carbon-fiber thermoplastic composites. To avoidcracking, techniques use relatively short rivets 160 to pierce into thesecond workpiece 120 as little as possible. Also to avoid cracking,materials having a relatively high ductility are typically used, whichlimits the options for use in the end product.

SUMMARY OF THE DISCLOSURE

Due to the aforementioned deficiencies, the need exists for rivetingsystems and methods to join workpieces securely, efficiently, andcost-effectively.

In various embodiments, the technology includes a riveting system foruse in mechanically linking adjacent workpieces by rivet. The systemincludes a protrusion having, in profile, opposing protrusion wallsegments extending in opposite directions from a peak toward respectivetransition points. The system also includes at least one trough having atrough surface comprising (i) a trough inner wall, extending from thetransition points to a trough bottom and (ii) a trough outer wall,extending from the trough bottom to a trough outer edge.

The opposing protrusion wall segments, in extending from the peak towardthe transition points, may extend from a dividing line in oppositedirections from the peak toward the transition points. And the troughouter wall may extend out farther at a section than the trough outeredge to, in operation of the die, force a rivet leg to bend so that arivet tip moves toward the dividing line.

In various embodiments, the protrusion extends farther in a directionthan a position of the trough outer edge, so that a proximate workpieceof the workpieces first contacts the protrusion of the die, not first ator directly adjacent the trough outer edge, when the proximate workpieceand the riveting first contact each other in operation of the rivetingdie.

The height of the protrusion is equal to or greater than a depth of thetrough in some cases.

In profile views of various implementations, an entirety of a surface ofthe trough is curved continuously and/or an entirety of a surface of theprotrusion is curved continuously.

The rivet and the die may be part of the same system, such as by beingsold or otherwise provided together for use in making the joint. Theworkpieces may also be part of a system with one or more rivets and/orwith the die.

The rivet may have a height greater than a sum of thicknesses, measuredalong a line of riveting, of the workpieces being linked, so that therivet can pass fully through the workpieces in operation of the system.

The technology in various embodiments includes a rivet-formed joint. Thejoint includes a first workpiece, a second workpiece, and the rivetincluding a rivet head and a rivet leg, wherein the rivet leg extends ina first direction through the workpieces, flares outward, in a seconddirection perpendicular to the first direction, and turns back toward athird direction generally opposite the first direction, forming amechanical hook, mechanically linking the first workpiece to the secondworkpiece.

The rivet leg, after extending in the first, second, and thirddirections, may extend in a fourth direction generally toward the rivethead.

An entirety of a side of the rivet leg, on a head-side of the rivet leg,is covered with workpiece of the second workpiece in someimplementations.

In some cases, a tip of the rivet is disposed within the secondworkpiece.

The portion of the second workpiece, behind—e.g., beneath—the rivet, ispipped in in some cases, having a convexity corresponding to a shape ofa rivet die used with the rivet to form the joint joining the first andsecond workpieces.

The rivet leg and material of the second workpiece may form a gap orspace between them that is closed when viewing the joint in a profileview.

The technology also includes a process for mechanically linking adjacentworkpieces using a rivet and a die. The process includes: positioning asecond workpiece in contact with the die; positioning the rivet,comprising a head and a leg having a distal edge or tip, adjacent afirst workpiece of the workpieces; and applying load to the rivet head,thereby forcing the distal tip to move in pre-determined manners. Thetip is forced to (i) pierce through the first workpiece, (ii) piercethrough the second workpiece, (iii) contact the die, first at a sidewall of a protrusion or an inner wall of a trough of the die, and thenalong the inner wall of the trough, (iv) flare outward upon reaching abottom of the trough, (v) flare outward and upward along a lower troughsurface toward an outer trough wall, and (vi) move upward along an outerwall of the trough, so that the leg forms a mechanical hook,mechanically linking the adjacent workpieces.

The load is applied generally along a load line and the rivet tip, afterflaring outward and moving upward, moves toward the load line in someimplementations.

The process further includes receiving, by a controller comprising aprocessor, from an input device, data indicating load and displacementvalues for the process.

The process can further include comparing, by the controller, the loadand displacement values to a pre-established load/rivet-displacementprofile.

The process can further include determining, based on results of thecomparing, whether riveting was performed properly.

In some implementations, the process includes initiating, if theriveting was not performed properly, one or both of: communicating analert and marking a joint arrangement formed by the riveting. Theprocess may include communicating the alert for receipt by personnel, ora computerized or at least electronic device, and/or marking the joinedproduct, such as by stamping or otherwise marking one of the workpiecesjoined, adjacent the apparently flawed joint or elsewhere.

Other aspects of the present technology will be in part apparent and inpart pointed out hereinafter.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conventional technique for joining workpieces.

FIG. 2 illustrates a first example riveting die for use in joiningworkpieces, according to embodiments of the present disclosure.

FIG. 3 illustrates workpieces being joined by a rivet using the die ofFIG. 2 and a punch machine, according to an embodiment of the presentdisclosure.

FIG. 4 illustrates the workpieces after being joined by the operationshown in FIG. 3, with the punch machine and die removed, with the rivetedge flared outward and upward.

FIG. 5 illustrates the workpieces after being joined by an operationsimilar to that shown in FIG. 3, except that the rivet edge is pushedinward after being flared outward and upward.

FIG. 6 shows an example load-displacement chart.

FIG. 7 shows an alternative hook mechanism.

FIG. 8 shows a controller specially configured for using force signalsfrom a riveting process to evaluate the process, including comparing thesignal to a pre-established load/rivet-displacement profile like that ofFIG. 6.

FIG. 9 shows example joint strength values for rivets of differentheights, with and without a washer.

FIG. 10 illustrates a second example riveting die for use in joiningworkpieces.

The figures are not necessarily to scale and some features may beexaggerated or minimized, such as to show details of particularcomponents. In some instances, well-known components, systems, materialsor methods have not been described in detail in order to avoid obscuringthe present disclosure.

DETAILED DESCRIPTION

As required, detailed embodiments of the present disclosure aredisclosed herein. The disclosed embodiments are merely examples that maybe embodied in various and alternative forms, and combinations thereof.As used herein, for example, exemplary, and similar terms, referexpansively to embodiments that serve as an illustration, specimen,model, or pattern.

References herein to how a feature is arranged can refer to, but are notlimited to, how the feature is positioned with respect to otherfeatures. References herein to how a feature is configured can refer to,but are not limited to, how the feature is sized, how the feature isshaped, and/or material of the feature. For simplicity, the termconfigured can be used to refer to both the configuration andarrangement described above in this paragraph.

Specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a basis for the claims and asa representative basis for teaching one skilled in the art to employ thepresent disclosure.

While the present technology is described primarily in connection withautomobiles, the technology is not limited to automobiles. The conceptscan be used in a wide variety of applications, such as in connectionwith aircraft and marine craft.

While the technology is described generally with respect to a verticallyfocused spatial context, wherein the rivet is forced initially generallyvertically downward into workpieces being connected, the descriptionsherein are not limited to this orientation. The descriptions thusinclude within their scope other spatial contexts, such as, for example,wherein the rivet is forced sideways, diagonally at any angle, or evenupward into the workpieces, with the die being positioned at an oppositeside.

I. OVERVIEW OF THE PRESENT TECHNOLOGY

The present technology includes novel dies, for use in joining parts, orworkpieces, using a novel mechanical hook.

The die is uniquely shaped to cause a distal edge or tip of the rivetto, after being forced through both workpieces, flare outward andupwards toward the workpieces being joined.

II. FIGS. 2, 3, AND 10

FIG. 2 illustrates a cross-sectional schematic of a first example die250 ¹ for use in joining workpieces, according to an embodiment of thepresent disclosure. FIG. 10 illustrates a cross-sectional schematic of asecond example die 250 ² for use in joining workpieces, according to anembodiment of the present disclosure. Each die is at times referred togenerically by numeral 250 herein.

The die 250 includes at least one guide trough 252. In variousembodiments, the guide trough 252 is generally circular. The trough 252is positioned adjacent a protrusion 254. In some implementations, thetrough 252 can be considered to form a mote around the protrusion 254.

In various embodiments, the protrusion 254 is the highest point on thedie 250, as shown in FIG. 2. The protrusion 254 is thus the firstportion of the die 250 to contact the second workpiece 120, when theworkpieces (e.g., material sheets) 110, 120 and the die 250 arepositioned adjacent one another.

In some implementations, the protrusion 254 is the only portion of thedie 250 that contacts the workpieces 110, 120. In other implementations,some of the lower workpiece material is pushed down to contact anintermediate point 265 ¹ or surface 265 ² adjacent the guide trough 252,opposite the protrusion 254, as shown in FIG. 3. The intermediate point265 ¹ and surface 265 ² are between or intermediate the higher elevationof a top of the protrusion 254 and the lower elevation of lower portionsof the trough 252.

In various embodiments, the protrusion 254 is partially or generallycurved. The protrusion 254 in some cases includes a generallyhemispherical portion. The protrusion 254 is not necessarily roundedperfectly in all places. In various embodiments, at least a portion of asurface 255 of the protrusion 254 is formed along one or more radii 257.As an example, the radius 257 can be in the range of about 1.5 mm toabout 2.0 mm.

The radius 257, like all die dimensions, can also be represented interms of another die dimension. For example, the radius is representedas a percentage, fraction, ratio, or multiple of overall die height,rivet height, workpiece(s) thickness(es), etc.

The guide trough 252 is partially or generally curved. In variousembodiments, at least a portion of a surface of a trough side 253(including 253 ₁ and 253 ₂) of each guide trough 252 is formed along oneor more radii 259.

In various embodiments, for use with thermoplastic workpieces 110, 120,for instance, the radius 259 can be in the range of about 0.7 mm toabout 1.0 mm.

The trough 252 includes an inside or interior wall 253 ¹ connected tothe side wall 256 of the protrusion 254.

As described more below, in use of the die 250, a distal edge or tip 312of a rivet 310 (FIG. 3) will, after being forced to pierce through theworkpieces 110, 120, first contact the die 250 at the trough inside wall253 ¹ or the protrusion side wall 256. In FIG. 3, the area including thehook and its distal tip 312 is called out by reference numeral 7,indicating that the area is shown in FIG. 7.

In some embodiments, the inside wall 253 ¹ is slightly rounded orgenerally flat. The trough inside wall 253 ¹ transitions to theprotrusion side wall 256. In some embodiments, the protrusion side wall256 is slightly curved or generally flat. In some embodiments in whichboth walls 253 ¹, 256 have curved portions, the respective curvedportions bend generally in opposite directions, with there being no bendat a point where the walls 253 ¹, 256 connect. The trough inside wall253 ¹ can, for instance, bend, even if very slightly, in an oppositedirection than the bend of the adjacent protrusion side wall 256.

The transition between the walls 253 ¹, 256 can occur at or adjacent anelevation of the die 250 corresponding to the intermediate point 265 ¹or surface 265 ².

The inside wall 253 ¹ of the trough 252 can extend with respect tovertical at any of a wide variety of angles 261. The angle 261 can alsoor instead be considered to describe an angle by which the wall 256 ofthe protrusion 254 extends with respect to vertical, and/or an angle ofthe die 250 at a transition between the inside wall 253 ¹ of the trough252 and the protrusion side wall 256, as can be appreciated by FIG. 2.While the die 250 can have other angles 261, here, in variousembodiments the angle 261 is between about 45 degrees and about 60degrees. Such angle range may be beneficial for implementations joiningthermoplastic workpieces. For implementations joining metal, forinstance, the angle 261 may be smaller, such as between about 35 degreesand about 50 degrees. For thermoplastic composites, it appearsbeneficial to have a larger relative angle 261, to flare the rivet legoutward more easily, then upward through the lower workpiece 120.

An area of the die 250 being at and/or adjacent the transition can bereferred to as an initial contact area, because the distal edge 312 ofthe rivet 310 will first contact the die 250 there during riveting.

In a contemplated embodiment (not shown in detail), the rivet 310includes multiple legs that join the workpieces 110, 120. A distal tipof each leg would be forced to pierce through the workpieces 110, 120and into contact with the die 250, at which point the legs would,starting at the tips, each flare outward, then upward, and possibly fromthere, slightly inward. The potential for rivet leg(s) to move inwardsome, after moving upward, is described further below.

The guide trough 252 includes a width 262. The width 262 can be measuredbetween an outer edge 263 of the trough 252 and an inner edge 264 of thetrough 252. The trough side 253 reaches the intermediate point 265 ¹ ofthe die 250 at the outer edge 263 of the trough 252.

While the guide trough 252 can have other widths 262 without departingfrom the present disclosure, in some embodiments the width 262 isbetween about 3 mm and about 4 mm. If the width 262 is too large,cracking may be promoted and/or damage to the distal edge of the rivet310.

For implementations in which metal is joined, the width 262 can be canbe the same or higher, such as between about 3 mm and about 5 mm. Itshould be appreciated that for all dimensions described herein, such aslengths, widths, and thicknesses, depend on the scale of implementation.For thicker workpieces, for instance, longer rivets 310 and larger die250 would be appropriate.

In a contemplated embodiment, the die 250 ² is configured so that theouter side 253 ² of the trough 252 moves upward, then turns inward atthe outer edge 263, as shown in FIG. 10. The outer wall 253 ² extendsfrom a bottom of the trough 252, generally upward, and then brieflytoward the protrusion 254.

The outer wall 253 ² of the die 250 (e.g., the first or second exampledie 250 ¹, 250 ²) extends at an angle 269 with respect to vertical.While the guide trough 252 can have other outer-wall angles 269 withoutdeparting from the present disclosure, in some embodiments theouter-wall angle 269 starts at about 90 degrees, adjacent a bottom ofthe trough 252 and bends or otherwise extends to about 180 degrees at oradjacent the outer edge 263. In embodiments like that shown in FIG. 10,the wall further extends at the edge 263 so that the angle 269 goesbeyond 180 degrees at or adjacent the outer edge 263. As can be seen,the trough outer wall extends beyond the trough outer edge 263. Or inother words, the outer edge 263 overlaps a portion of the outside wall253 ², and in some cases overlaps a portion of the trough bottom. Inoperation of the die 250 ², this geometry forces a rivet leg 314 to bendso that the rivet distal edge 312 moves toward a dividing line of theriveting die. The dividing line can be, for instance, a center lineextending through the protrusion, vertically in the example views shown,such as the dividing line shown in FIG. 2.

The protrusion 254 includes a width 266 (FIG. 2). The width 266 can bemeasured between central-portion edges, where the protrusion 254 reachesthe intermediate surface 265. While the protrusion 254 can have otherwidths 266 without departing from the present disclosure, in someembodiments the width 266 is between about 2 mm and about 2.5 mm.

For implementations joining metal workpieces 110, 120, the width 266 canbe the same or higher, such as between about 2 mm and about 3 mm. Forthermoplastic composites, the width 266 could be smaller, such as below2 mm or within a range including the lower end of the 2-3 mm range, tominimize the cracking of the dismal edge of the rivet 310.

Each protrusion 254 includes a height 267 (FIG. 2), measured, in someimplementations, from the intermediate point 265 ¹ or surface 265 ² to apeak or tip of the protrusion. The protrusion 254 is convex, extendingabove the intermediate point 265 ¹ or surface 265 ². In a contemplatedembodiment the height is measured from about the transition point 264 tothe peak of the protrusion 254.

The protrusion 254 can be configured and arranged in the die 250 so thatwhen the workpieces 110, 120 are placed on the die 250, contacting theprotrusion 254, and pressure applied on the workpieces (e.g., arrow 133and/or arrow 180 in FIG. 3), the protrusion 254 pips, or is pushed, upinto the lower workpiece 120. The resulting position is shown by way ofexample in FIG. 3.

The pipping promotes flaring or forking of distal ends of the rivet legs314, forming rivet feet. The feet, when pushed outward and upward, forma mechanical hook, to mechanically lock the two workpieces 110, 120together.

While the protrusion 254 can have other heights 267 without departingfrom the present disclosure, in some embodiments, the height 267 isbetween about 0.2 mm and about 0.4 mm.

For implementations joining metal workpieces 110, 120, the height 267can be the same or larger, such as between about 0.25 mm and about 0.5mm. For joining thermoplastic-composite workpieces 110, 120, a lowerrelative height 267, such as below 0.2 mm, or a range including a lowerend of the 0.25-0.5 mm range, could minimize upsetting of any of therivet 130 (e.g., walls or side of the rivet) and connection between therivet 130 and one or more of the workpieces 110, 120.

Each trough 252 includes a depth 268, measured, in some implementations,from an intermediate surface 265. While the trough 252 can have otherdepths 268 without departing from the present disclosure, in someembodiments the depth 268 is between about 1.0 mm and about 2.0 mm.

For implementations joining metal workpieces 110, 120, the depth 268 canbe larger, such as between about 1.5 mm and about 2.2 mm. Forthermoplastic composite, a smaller depth, such as below 1.5 mm or withina range including a lower end of the 1.5-2.2 mm range, may help avoidcracking of the lower workpiece 120.

The height 267 of the protrusion 254 and the depth 268 of the trough 252can be defined as ratios of each other. For instance the height 267 anddepth 268 in various embodiments have a one-to-one (1:1) ratio, whereinthe height and depth are the same. In some embodiments, the height 267is greater than the depth, such as by being 1.2, 1.3, 1.4 or 1.5 timesgreater the depth 268.

For various implementations in which metal workpieces 110, 120 arejoined, the height 267 is smaller than the depth 268. For example, aratio of the height to the depth 268 can be between about 1:9 and about1:3—for instance, the height 267 being about 0.25 mm and the depth beingabout 0.5 mm. A larger ratio may minimize cracking of the lowerworkpiece 120 and minimize upsetting of the rivet in riveting (e.g., ofthermoplastic composites)—the ratio can be, for instance, between about1:5 and about 1:2.5.

III. FIGS. 3, 5, 7, AND 10

FIG. 3 illustrates schematically a cross section of a rivet-joiningsystem 300 in use joining the first workpiece 110 to the secondworkpiece 120. While the present disclosure describes primarilyconnecting two workpieces 110, 120, the disclosure encompassesembodiments in which more than two workpieces are connected by the rivetand the die of the present technology.

The workpieces 110, 120 can each include one or more materials, and invarious embodiments include the same material(s) as each other, ordifferent material(s). Example materials include polymeric composites,such as a carbon-fiber reinforced nylon composite, and include one ormore metals, such as aluminum.

The system 300 includes a riveting machine 302. The machine 302 invarious embodiments can be like the machine 130 described above inconnection with FIG. 1, having a body 132 and a piston or punch 134positioned adjacent and movably with respect to the machine body 132. Inother embodiments, another source of riveting force, such as a person orother machine (e.g., robotic machine), sufficient for performing neededpunching or pushing function, is used.

The system 300 includes the novel die 250 and a novel rivet 310. Invarious embodiments, the die 250 is a stand-alone sub-system or systemthat can be provided with one or more rivets 310. In variousembodiments, the rivet 310 is a stand-alone sub-system or system thatcan be made and/or sold on its own or with the die 250.

In operation, the machine body 132 is positioned adjacent a firstworkpiece 110, and can be arranged to contact or apply downward force onthe workpiece 110, as indicated by arrow 133 in FIG. 3.

The rivet 310 is positioned beneath the punch 134 and above theworkpieces 110, 120. The punch 134 strikes or is otherwise pushed downon the rivet 310, as indicated by arrow 180, forcing the distal edge 312of the leg 314 of the rivet 310 to pierce the workpieces 110, 120—firstthrough a proximate one 110 of the workpieces 110, 120, beyond aninterface 115 between the two workpieces 110, 120, and on into a distalone 120 of the workpieces.

The area in FIG. 3 including the hook and its distal tip 312 is calledout by reference numeral 7, indicating that the area is shown in FIG. 7.

In some implementations, depending on characteristics of the system(e.g., workpiece material, thickness, rivet dimensions, etc.), some ofthe lower workpiece 120 is pulled down with, or otherwise displaced bymovement of, the rivet 310, below a lower surface 122 of the workpiece120. Material indicated by reference numeral 316 in FIG. 3 includes thisdisplaced material.

In some embodiments, a washer or shim (not shown) is positioned betweena portion of the rivet (e.g., rivet head) and the workpiece.Additionally or alternatively, a larger (e.g., wider) rivet head can beused for similar purposes. Purposes include distributing more broadlyany forces being transferred from the rivet 310 to the workpieces 110,120. The shim bears load that would otherwise be passed to the adjacentworkpiece 110. By distributing the forces, the workpieces 110, 120, orat least the upper workpiece 110 is put under less stress during theriveting. Joints resulting from the larger head or shim can be strongerthan those formed without the larger head or shim. The benefit isdescribed more below in connection with FIG. 9.

While the rivet 310 can include other materials without departing fromthe scope of the present disclosure, in various embodiments the rivet310 includes a metal such as steel (austenitic or martensitic),aluminum, or copper, thermoplastics, any composite, alloy, the like, orother.

The die 250 and/or the rivet 310 are/is configured (e.g., height, shape)so that the rivet 310, after being forced through both workpieces 110,120, contacts the trough 252 and, in response to the contact, flaresoutward and then upwards toward the workpieces 110, 120, such asdepicted in FIG. 3. As provided, the die 250 configuration promotingflaring can include the protrusion 254 extending above an intermediatepoint 265 ¹ or surface 265 ².

While the rivet 310 can have other heights—measured prior to piercing,from a top of rivet head 311 to the rivet distal edge 312—withoutdeparting from the scope of the present disclosure, in variousembodiments the rivet 310 has a height between about 8 mm and 15 mm.Generally, the rivet height can be selected based on factors including athickness of the workpieces being joined and dimensions of the die 250.

In some embodiments, the rivet 310 has pointed distal edges 312 to limitstress on the workpieces 110, 120 in piercing. The edges 312 arepreferably as sharp as possible for this purpose.

In one aspect, one or both workpieces 110, 120 are pre-heated to softenthe material prior to riveting, thereby reducing stress caused by theriveting.

The rivet dimensions and materials, including leg thicknesses, areconfigured according to required performance characteristics. Thedimensions, and material, are selected so that the leg 314 hassufficient strength to withstand the initial piercing, and sufficientductility to flare and bend after the piercing. The dimensions andmaterials are also selected to promote a robust, strong resulting joint.The dimensions and material should be selected so that the mechanicalhook formed is strong, for instance.

The rivet height can be represented by various ratios. The height canbe, for instance, between about 1.5 and about 2 times the combinedthicknesses of the workpieces 110, 120 being joined. The ratio in someimplementations is even greater.

While the workpieces 110, 120 can have other thicknesses (measuredvertically in FIG. 3) without departing from the scope of the presentdisclosure, in various embodiments each has a thickness of about 2.5 mm.In various embodiments, each has a thickness of between about 2.0 mm andabout 3.0 mm.

The hook mechanism 315 fostered by the flaring creates a mechanicallock, beyond other mechanical connections between the rivet 310 and theworkpieces 110, 120, such as friction between the workpieces 110, 120and intermediate portions of the rivet legs 314. The hook mechanism 315may pinch material of the lower workpiece 120 and/or push material ofthe lower workpiece 120 upward in the riveting process. Such material isindicated by reference numeral 316 in FIGS. 3 and 7.

As described above, the outer wall 253 ² extends or bends generallyupward along a line, or has a tangent, being at an angle 269 (FIG. 2).The angle 269 is in various embodiments about 180 degrees in associationwith at least one point of the outer wall 253 ². As provided, in acontemplated embodiment, the outer wall 253 ² further extends or bendsbeyond vertical, to an angle 269 greater than 180 degrees, as shown inFIG. 10.

The rivet 310 in such implementations can have sufficient configuration(e.g., have sufficient height), and the die 250 configured (e.g.,dimension) so that the distal edge 312 is forced to flare out, by theinside wall 253 ¹ and bottom of the trough 252, upward by the outsidewall 253 ². In some implementations, the distal edge 312 can to someextent extend laterally, back toward the protrusion 254. An exampleresulting connection is shown in FIG. 5. The rivet leg 314 can turninward in some embodiments, even if the trough edge 263 does not curlinward like the die 250 ² shown in FIG. 10.

In various embodiments, the hook mechanism 315, when formed, partiallysurrounds and supports a portion 316 of the material of the secondworkpiece 120. In the vertical context, the material 316 would be abovethe hook mechanism 315. In any orientation, material 316 of theworkpiece 120 can be considered to be on a rivet-head side of the hookmechanism 315.

In these ways, the hook mechanism 315 creates a robust mechanicalconnection between the rivet 310 and the workpieces 110, 120, andbetween the workpieces 110, 120 being joined. The resulting connectionsare greater than those created by conventional riveting techniques.

In a contemplated implementation, the die 250 and rivet 310 areconfigured so that a gap 700 (FIG. 7) is formed between the rivet leg314 and the second workpiece 120 as the distal edge 312 is pushedthrough the workpiece 120, flared outward and upward. The gap 700 canbecome closed in this way.

The gap 700 can, after the gap is formed by the hook mechanism 315, bereduced in size, or be substantially eliminated, if the distal edge 312of the rivet 310 continues to be forced into the second workpiece 120.As shown in the profile view of FIG. 3, the gap or space may be closed.

IV. FIG. 4

FIG. 4 illustrates the workpieces 110, 120 joined by the operation shownin FIG. 3, after the workpieces are removed from the punch machine 302and die 250.

A depression in the lower workpiece 120, or both workpieces 120, 110,formed by the protrusion 254 of the die 250 pipping into the secondworkpiece 120, as described above, is referenced by numeral 400 in FIG.4. Reference numeral 401 calls out some of the material of the lowerworkpiece 120 pushed up by the protrusion of the die.

V. FIG. 5

FIG. 5 illustrates the workpieces 110, 120 joined by an operation likethat shown in FIG. 10, or like that shown in FIG. 3 wherein the rivet310 and the die 250 are configured so that the distal edge 312 of therivet 310 flares generally laterally outward, then generally upward, andthen further generally laterally inward, as described above.

VI. FIGS. 6-8

FIG. 6 shows an example load/rivet-displacement chart 600, showing arelationship between an input force, or load, applied to the rivet 310during riveting, and rivet displacement into the workpieces 110, 120.The y-axis 602 represents load or force, applied on the rivet, and thex-axis 604 represents rivet displacement. The example load-displacementprofile or signature is indicated by reference numeral 601.

Riveting processes can be evaluated or monitored in real time bycomparing feedback signal or data indicating actual load anddisplacement during each riveting to a load-displacement profile 601.

The feedback can be received at a performing controller or computer fromsensors or other components being part of or connected to the rivetingmachine 302. A component (e.g, sensor) can be configured to sensedisplacement of the piston or punch 134, for instance, which correlatesto rivet displacement. A component can also be configured to sense anamount of load required, or being transferred to the rivet 310 in order,to push the rivet 310 at each instance. When resistance to pushing therivet 310 increases, the height of the profile line 601 increases.

Many existing riveting machines, such as servo machines, outputdisplacement values as part of their normal operation. An examplecomponent measuring load is a load cell, or pressure or forcetransducer.

The load-displacement profile 601, like all terms used in the presentdisclosure, can be replaced by similar words. Other terms includeforce-displacement profile, force-displacement signature, andload-displacement signature. The profile 601 can be created in any of avariety of ways, including by test riveting or computer computationssuch as including a simulation.

With further reference to the example signature 601 of FIG. 6, theriveting process can be divided into four (4) primary phases, which canoverlap to some degree: establishment or clamping 606, piercing 608,flaring 610, and interlocking 612.

In the establishment phase 606, the riveting machine 302 engages therivet 310 and begins to apply load. In this phase, the machine 302begins to apply load on the rivet 310 towards overcoming staticimpediments to piercing such as surface tension atop of the firstworkpiece 110. Accordingly, rivet displacement is initially nil to low,and begins to increase as the process proceeds into the piercing phase608.

In the piercing phase 608, sufficient load is applied to the rivet 310to force rivet legs 314 to pass through the first workpiece 110, andthen the second workpiece 120. In the piercing phase 608, the distaledge 312 of the leg 314 passes completely through the second workpiece120, toward a bottom of the die trough 252. A slope of the protrusion254 can guide the distal edge 312 of the leg 314 into the trough 252.

With continued load from the riveting machine 302, the flaring phase 610begins. In the flaring phase 610, the distal edge 312 flares out,laterally outward along the die trough inner wall 253 ¹. The flaringcontinues along lower portions of the trough 252, and eventually theouter wall 253 ² of the trough 252.

After or toward the end of the flaring, the interlocking phase 612begins.

The dashed portion 613 of FIG. 6 shows how the signature 601 varies inthe novel interlocking phase 612 from the slope pattern developed in thepreceding two phases 608, 610. More particularly, the signature 601includes a unique dip 615 corresponding to a stage of the rivetingprocess in which the distal edge 312 of the rivet 310 passes out of thelower workpiece 120. At that point, displacement continues whilerequired force decreases.

After the rivet edge 312 exits the workpiece 120 (starting the dip 615),the rivet 310 engages the side of the protrusion 254 or trough 252. Withthe engagement, the required force on the rivet 310 to continue rivetdisplacement increases accordingly, and is indicated by the increase ofthe force value at ramp up 617.

In the ramp up 617, the rivet leg 314 is flared outward, and thenupward, and in some cases also then inward.

The analyzing controller can be a specially configured computing device,configured with code causing a processor of the controller to performthe comparison. An example controller 800 is shown in FIG. 8 anddescribed further below.

In determining whether a present riveting was performed properly, thecontroller 800 compares an actual load-displacement profile for thepresent riveting to the pre-established load-displacement profile shownat 601 or another such pre-set load-displacement profile. The comparisondoes not need to include comparing all parts of an actualload-displacement profile for the present riveting to thepre-established load-displacement profile 601. The comparisondetermines, for instance, whether the actual load-displacement profileincludes the dip 615 described. If it does not, then the rivet 310 maynot have pierced through the lower workpiece 120 for some reason.Example reasons include the selected rivet being too short or the rivetbeing too soft to pierce through one or both workpieces 110, 120. Asanother example, the rivet leg 314 may for some reason have flared whilethe edge 312 was still within the first or second workpiece 110, 120,instead of after having passed through both workpieces.

Further in determining whether a present riveting was performedproperly, the controller 800 can determine whether the actualload-displacement profile includes the ramp back up 617 described. If itdoes not, then the rivet 310 may not have flared and hooked for somereason. Example reasons include a rivet tip breaking, or unintendedabsence of the die.

In various embodiments, the comparison includes determining whether thedip 615 and the ramp up 617 are present, or whether a dip 615 and a rampup 617 identified have sufficient shape (e.g., slope, magnitude). Thedetermining can in some implementations be performed without literallycomparing the actual profile to the pre-established profile. Thepre-established profile can be represented in other ways, for instance,such as data points, thresholds, or the like, that actual rivetingload-displacement data can be compared to in order to determine whetherthe dip 615 and ramp up 617 are present, or whether a dip 615 and a rampup 617 identified have satisfactory shape.

The controller 800 can be configured to, in response to determining thatthe actual load-displacement of a present riveting does not match thepredicted load of the pre-determined load-displacement profile 601,and/or simply that the dip 615 and ramp up 617 was not present orsufficiently present—i.e., that the rivet did not become positioned asplanned—initiate provision of a notification or alert. Example alertactions include transmitting a fail or warning signal a light or otherdisplay device of the system, or to another computing device and/orlocal personal device, in any of these cases causing a light toilluminate or speaker to sound, for instance.

In a contemplated embodiment, a part failing the comparison is tagged ormarked to indicate insufficient joining. The indication can be arrangedto indicate the area of the questionable rivet, such as by a stamp orworkpiece indentation.

The controller 800 can be implemented in any of a variety of ways,including by being a part of any of a wide variety of greater systems801, such as a laptop, tablet, other mobile communications device, or ariveting robot or other machine. Although connections are not shownbetween all of the components illustrated in FIG. 8, the components caninteract with each other to carry out system functions.

As shown, the specially configured controller 800 includes a memory, orcomputer-readable storage device 802, such as volatile medium,non-volatile medium, removable medium, and non-removable medium. Theterm computer-readable media and variants thereof, as used in thespecification and claims, refer to tangible or non-transitory,computer-readable storage devices.

In some embodiments, storage media includes volatile and/ornon-volatile, removable, and/or non-removable media, such as, forexample, random access memory (RAM), read-only memory (ROM),electrically erasable programmable read-only memory (EEPROM), solidstate memory or other memory technology, CD ROM, DVD, BLU-RAY, or otheroptical disk storage, magnetic tape, magnetic disk storage or othermagnetic storage devices.

The specially configured controller 800 also includes a computerprocessor 804 connected or connectable to the computer-readable storagedevice 802 by way of a communication link 806, such as a computer bus.

The processor 804 could be multiple processors, which could includedistributed processors or parallel processors in a single machine ormultiple machines. The processor can be used in supporting a virtualprocessing environment. The processor could include a state machine,application specific integrated circuit (ASIC), programmable gate array(PGA) including a Field PGA, or state machine. References herein toprocessor executing code or instructions to perform operations, acts,tasks, functions, steps, or the like, could include the processorperforming the operations directly and/or facilitating, directing, orcooperating with another device or component to perform the operations.

The computer-readable storage device 802 includes the aforementionedcomputer-executable instructions, or code 808. The computer-executableinstructions 808 are executable by the processor 804 to cause theprocessor, and thus the specially configured controller 800, to performany combination of the computing functions described in the presentdisclosure.

The specially configured controller 800 further comprises aninput/output (I/O) device 810, such as a wireless transceiver and/or awired communication port. In some embodiments, the processor 804,executing the instructions 808, sends and receives information, such asin the form of signals, messages or packetized data, to and from one ormore communication networks 812, such as an intranet or internet, forcommunicating riveting process or riveting machine data to anothercomputer.

The specially configured controller 800 includes or is connected to oneor more local input/output devices 814, including at least one localinput device 816 and/or one or more local output devices 818. The inputs816 can include the sensors or components measuring actual loads anddisplacements in rivetings, as mentioned. Local output devices 818 caninclude a separate local computing system or an automated system, suchas the riveting machine 302 or robotics equipment controlling theriveting, placement of one or more subject implements (e.g., workpiecesand/or rivets), and/or moving the resulting joined workpieces. Outputsto the device(s) 818 can also include the alert structure mentionedabove.

VII. FIG. 9

As discussed above, a washer or shim can be positioned between a portionof the rivet (e.g., rivet head) and the workpiece, when the rivet ispunched into the workpieces. Additionally or alternatively, a largerrivet head can be used for similar purposes—to distribute more broadlyany forces being transferred from the rivet to the top workpiece 110.The shim or larger head can keep the rivet 310 from digging into theadjacent workpiece 120. By distributing the forces, the workpieces 110,120, or at least the upper workpiece 110 is put under less stress in theriveting.

FIG. 9 shows a chart 900 of example joint strength values for rivets ofdifferent heights, and with and without a washer.

For preparing the chart 900, an amount of force required to separate ajoint after it is formed using the various rivets, and with and withouta washer, was measured. The y-axis 902 represents the amount ofseparation force. In the example testing, the separation force ismeasured in kilonewtons (kN).

The various rivet arrangements are arranged along the x-axis 904. Thearrangements include data 906 for a 7 millimeter (mm) rivet, data 908for an 8 mm rivet, data 910 for a 9 mm rivet, data 912 for a 10 mmrivet, and data 914 for an 11 mm rivet.

The solid columns represent the separation forces for the respectiverivets when a washer or shim is not used. The hashed columns representsthe separation forces for the rivets when a washer is used.

The I bars at the top of each column indicate a range, or margin oferror, resulting from various measurements.

As shown, the tests indicate that joints were stronger when a washer orshim is used over a base rivet head size. It is contemplated that thesame, similar, or better results would follow using a rivet head that islarger, such as having the size corresponding to the shim, as comparedto the base size.

As also shown, the tests indicate that joints were stronger when alonger rivet was used, such as a rivet presenting a greaterrivet-to-workpiece thickness ratio. It is contemplated that this effectresults at least, in part, to the increased footing created by a largermechanical hook. Once the rivet has pierced through the second workpiece120, stress on the workpieces 110, 120 is greatly reduced. Thus, thebenefits of additional joining activity after the pierce-through areenjoyed with little or no weakening of the workpieces 110, 120. While alonger rivet has been found advantageous, it is contemplated that thereare limits, including space limitations to using still longer rivets,and expected that there is an ideal height, longer than traditionalrivets for joining workpieces, can be determined by a designercorresponding to each context—e.g., workpiece thickness, material, etc.

VIII. SELECT BENEFITS OF THE PRESENT TECHNOLOGY

Many of the benefits and advantages of the present technology aredescribed above. The present section restates some of those andreferences some others. The benefits described are not exhaustive of thebenefits of the present technology.

Connection between the rivet 310 and workpieces 110, 120 is greater thanconnections possible using conventional riveting techniques. Connectionfostered between the workpieces 110, 120 is also greater thanconnections possible using conventional riveting techniques.

Overall static strength of the resulting joint (e.g., FIG. 4) isincreased markedly as compared to prior techniques. The higher strengthresults from a number of factors, such as the mechanical hook formedand, in some embodiments, the shim or larger head used.

Potential for cracking in the lower workpiece 120 between the rivet 310and an edge of the workpiece 120 (e.g., 117 in FIG. 1) is eliminated orat least greatly reduced as compared to some prior techniques. Less orno cracking can be promoted by having rivet legs 314 flare after therivet distal edge 312 exits the lower workpiece 120, as compared toconventional techniques in which the distal edge never leaves the secondworkpiece 120 and, thus, if the rivet leg flares, the distal edge of therivet flares while still in the workpiece 120. Less or no cracking canalso be promoted by using sharper rivets (e.g., ultra-sharp rivetedges). Less or no cracking can also be promoted by using shims orrivets with larger heads. An ancillary benefit of the present techniquesallowing less or no cracking, is that less-ductile materials can be usedas compared with many prior techniques, which were limited to usingmaterials of relatively high ductility.

IX. CONCLUSION

Various embodiments of the present disclosure are disclosed herein. Thedisclosed embodiments are merely examples that may be embodied invarious and alternative forms, and combinations thereof.

The above-described embodiments are merely exemplary illustrations ofimplementations set forth for a clear understanding of the principles ofthe disclosure.

Variations, modifications, and combinations may be made to theabove-described embodiments without departing from the scope of theclaims. All such variations, modifications, and combinations areincluded herein by the scope of this disclosure and the followingclaims.

What is claimed is:
 1. A riveting system, for use in mechanicallylinking adjacent workpieces by a rivet, comprising: a die having aprotrusion, at least one guide trough adjacent to the protrusion, and anintermediate surface adjacent to the guide trough opposite theprotrusion; the protrusion having, in profile, opposing protrusion wallsegments extending in opposite directions from a peak toward respectivetransition points; the at least one guide trough having a trough surfacecomprising (i) a trough inner wall, extending from the transition pointsto a trough bottom and (ii) a trough outer wall, extending from thetrough bottom to a trough outer edge, the trough outer wall turninginward at the trough outer edge such that the trough outer wall extendsinto the die beyond the trough outer edge; and the intermediate surfaceextending laterally from the trough outer edge and establishing anintermediate elevation of the die, wherein the protrusion extends abovethe intermediate surface and the trough outer edge to a higher elevationthan the intermediate elevation of the die, the peak of the protrusionextending above the intermediate surface to a protrusion height and thetrough bottom extending below the intermediate surface to a troughdepth, and wherein the protrusion height is greater than the troughdepth.
 2. The riveting system of claim 1, wherein: the opposingprotrusion wall segments, in extending from the peak toward thetransition points, extend from a dividing line in opposite directionsfrom the peak toward the transition points.
 3. The riveting system ofclaim 1, wherein, in profile, an entirety of a surface of the trough iscurved continuously.
 4. The riveting system of claim 1, wherein, inprofile, an entirety of a surface of the protrusion is curvedcontinuously.
 5. The riveting system of claim 1, further comprising therivet.
 6. The riveting system of claim 5, wherein the rivet has a heightgreater than a sum of thicknesses, measured along a line of riveting, ofthe workpieces being linked, so that the rivet can pass fully throughthe workpieces in operation of the system.
 7. The riveting system ofclaim 1, wherein the at least one guide trough encircles the protrusion.8. The riveting system of claim 1, wherein the protrusion ishemispherical.
 9. A riveting system, for use in mechanically linkingadjacent workpieces by a rivet, comprising: a die having a protrusion,at least one guide trough adjacent to the protrusion, and anintermediate surface adjacent to the guide trough opposite theprotrusion; the protrusion having, in profile, opposing protrusion wallsegments extending in opposite directions from a peak toward respectivetransition points; the at least one guide trough having a trough surfacecomprising (i) a trough inner wall, extending from the transition pointsto a trough bottom and (ii) a trough outer wall, extending from thetrough bottom to a trough outer edge; and the intermediate surfaceextending laterally from the trough outer edge and establishing anintermediate elevation of the die, and wherein the protrusion extendsabove the intermediate surface and the trough outer edge to a higherelevation than the intermediate elevation of the die, the peak of theprotrusion extending above the intermediate surface to a protrusionheight and the trough bottom extending below the intermediate surface toa trough depth, and wherein the protrusion height is greater than thetrough depth.
 10. The riveting system of claim 9, wherein the troughouter wall turns inward at the trough outer edge such that the troughouter wall extends into the die beyond the trough outer edge.
 11. Theriveting system of claim 9, wherein the protrusion is hemispherical.